Rhodopirellula lusitana sp. nov. and Rhodopirellula rubra sp. nov., isolated from the surface of macroalgae.

Twenty two strains of Rhodopirellula were isolated from the epiphytic community of several marine macroalgae and separated into two groups, designated as group B and group C. In this study, we characterized these groups as two novel species belonging to the genus Rhodopirellula. These strains were represented by pleomorphic cells that were arranged in rosettes and formed pink- or red-pigmented colonies. The organisms were chemoorganotrophic and required vitamin B12 for growth. Their optimal temperature for growth was around 25°C. Major fatty acids were C18:1 ω9c, C16:0 and C16:1 ω7c/C16:1 ω6c. Phosphatidylcholine and phosphatidylglycerol were the major polar lipids. Unidentified phospholipids were also present. The 16S rDNA sequence analysis confirmed the affiliation of these organisms to the order Planctomycetales, genus Rhodopirellula, with R. baltica as the closest phylogenetic relative. The analysis of a partial sequence of the gene encoding the β-subunit of RNA polymerase (rpoB) confirmed the phylogenetic separation of the isolates into two different species of the genus Rhodopirellula. The 16S rRNA sequences from strains of group B revealed their widespread occurrence across the world, whereas strains of group C were not observed before. On the basis of physiological, biochemical, chemotaxonomic and genetic characteristics we propose that our isolates represent two new species of Rhodopirellula, Rhodopirellula rubra sp. nov. (type strain is LF2(T)=DSM 25,459=CECT 8075) and Rhodopirellula lusitana sp. nov. (type strain is UC17(T)=DSM 25,457=LMG 27,777).